日期类 class_Date

#define _CRT_SECURE_NO_WARNINGS 1#include<iostream>using namespace std;class Date{friend ostream& operator<<(ostream& out, const Date& d);friend istream& operator>>(istream& in, Date& d);public://构造Date (int year = 1900, int month = 1, int day = 1):_year(year),_month(month),_day(day){;}//拷贝构造Date (const Date& d):_year(d._year),_month(d._month),_day(d._day){;}void Display(){cout<<_year<<"-"<<_month<<"-"<<_day<<endl;}//判断该月天数//静态成员函数只能调静态函数，不能访问私有成员，因为没thisstatic int GetMonthDays(int year, int month){//年月不合法返回-1，注：不能用IsInvalid判断，否则就会递归GetMonthDaysif (year <1900 || month < 1 || month > 12){return -1;}static int arr[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};int days = arr[month];if (month == 2 && IsLeapYear(year)) //月份判断开销小，放前面{days++;}return days;}//判断闰年static bool IsLeapYear(int year){return ((year%4 == 0)&&(year%100 != 0)) || (year%400 == 0);}//判断日期是否合法bool IsInvalid(){return (_year >= 1900 && _month > 0 && _month < 13 && _day > 0 && _day <= GetMonthDays(_year, _month));}bool operator>(const Date& d) const {if (_year > d._year){return true;}else if(_year == d._year){if (_month > d._month){return true;}else if (_month == d._month){if (_day > d._day){return true;}}}return false;}bool operator==(const Date& d) const {return (_year == d._year)&& (_month == d._month)&& (_day == d._day);}Date operator+(int day) const{if (day < 0){return *this - (-day);}Date tmp(*this);tmp._day += day;while(!tmp.IsInvalid()){tmp._day -= GetMonthDays(tmp._year, tmp._month);tmp._month++;if (tmp._month == 13){tmp._year++;tmp._month = 1;}}return tmp;}Date operator-(int day) const{if (day < 0){return *this + (-day);}Date tmp(*this);tmp._day -= day;while(!tmp.IsInvalid()){tmp._month--;if (tmp._month == 0){tmp._year--;tmp._month = 12;}tmp._day += GetMonthDays(tmp._year, tmp._month);}return tmp;}bool operator!=(const Date& d) const{return !(*this == d);}Date& operator=(const Date& d){_year = d._year;_month = d._month;_day = d._day;return *this;}bool operator<(const Date& d) const{return !(*this > d || *this == d);}Date& operator+=(int day){*this = *this + day;return *this;}Date& operator++()//前置++，后返回{*this += 1;return *this;}Date operator++(int) //后置++，先返回{Date tmp(*this);tmp += 1;return tmp;}//日期-日期int operator-(const Date& d) const{Date min(*this);Date max(d);int tag = -1;int count = 0;if (d < *this){min = d;max = *this;tag = 1;}while(min != max){//后置++调了4次构造//前置++调了2次构造，高效++min;count++;}return count*tag;}private:int _year;int _month;int _day;};ostream& operator<<(ostream& out, const Date& d){out<<d._year<<"-"<<d._month<<"-"<<d._day<<endl;return out;}istream& operator>>(istream& in, Date& d){cout<<"输入年月日"<<endl;in>>d._year;in>>d._month;in>>d._day;return in;}int main(){Date a;cin>>a;cout<<a<<endl;return 0;}